Unable to add item" and "that item is not available" Error

Site URL: https://pitcherbuddy.com/

I am using the Cacao template(https://www.squarespace.com/templates/cacao) for one of our clients. It's been a while since any changes have been made, but for some reason the Add to Cart button no longer works. Gives the error Unable to Add Item. Any idea why? 

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Got it, thanks!